The need to reduce fuel consumption and emissions in automobiles and other vehicles is well known. Therefore, vehicles are being developed that reduce reliance or completely eliminate reliance on an internal combustion engine. Electrified vehicles are one type of vehicle currently being developed for this purpose. In general, electrified vehicles differ from conventional motor vehicles in that they are selectively driven by one or more battery powered electric machines. Conventional motor vehicles, by contrast, rely exclusively on the internal combustion engine to drive the vehicle.
Stop/start vehicles are also being developed to reduce fuel consumption and emissions by shutting down the engine during portions of the drive cycle. For example, a stop/start vehicle can turn its engine off while the vehicle is stopped rather than allow the engine to idle. The engine is subsequently restarted when the accelerator pedal is depressed or when the vehicle is otherwise able to progress.
It may be desirable to save additional energy during the drive cycle of a vehicle. One manner of achieving additional energy savings is to spin down the transmission input shaft of the vehicle transmission when the vehicle is in Park or Neutral. The transmission pump typically cannot pressurize fast enough to smoothly engage the clutches of the transmission when a shift change is subsequently requested. Although some vehicles may be equipped with auxiliary oil pumps, these pumps lack sufficient capacity to generate the pressure or flow required to perform the initial engagement/filling of the clutches of the transmission.